The present invention relates to the transmission of optical signals and in particular to the multiplexing of a plurality of optical signal channels.
The currently most widely used approach to multiplexing optical signal channels is to assign a frequency range to each of the channels, and so to choose the ranges as not to overlap. This approach, obviously, requires the use of a considerable portion of the available spectrum for the accommodation of only a relatively small number of optical signal channels. Moreover, since the respective ranges may drift with time, it is necessary either to so select the widths of the ranges that the optical signal channels will not run into one another even under the worst case conditions, or to accept a certain amount of persistent interference between the channels. The latter alternative is usually unacceptable, so that the number of channels which can be multiplexed for transmission through a common optical path is further reduced due to the broadening of the ranges dedicated to the individual channels.